Mogul Base Lights Bulbs: What Are They?


It’s about the larger base. Mogul (screw) base light bulbs or mogul base

mogulblogbulbs have larger screw bases (E39) than the standard, medium (E26) screw base bulbs. In fact, the “39” of E39 and “26” of E26 each refer to the millimeter width of the respective screw bases (i.e., E39 base bulbs = 39 millimeters = 1.5 inches; and E26 base bulbs = 26 millimeters = 1.0 inch), and do not refer to the shapes of the light bulbs.

More power, more heat. Mogul base bulbs are made of cast porcelain to tolerate higher temperatures, making them ideal for industrial and commercial uses (e.g., power ratings of 250-1000 watts); in terms of technology, mogul base LED bulbs, mogul base compact fluorescent bulbs, and mogul base halogen, mercury vapor, metal halide, and high pressure sodium bulbs are available in the market.

“U” stands for mogul base. Selecting the correct size bulb can be confusing because light bulbs in general are available in different base sizes. All you have to remember when reading product descriptions is this: the “U” in, for example, M175/U/MED and MH1000/U/BT56, stand for mogul base. But if you happened to get a medium base bulb (E26) for your mogul base lamp (E39), the good news is that you can get a reducer to use the E26 light bulb on your E39 base bulb lamp; additionally, you can get a converter to use a 3-way E26 light bulb in a 3-way E39 base bulb lamp.

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17 thoughts on “Mogul Base Lights Bulbs: What Are They?

  1. Tim Rawhouser says:

    Amazing, discovered your site on digg.Happy I finally tested it out. Not sure if its my Safari browser,but sometimes when I visit your site, the fonts are really small? Anyway, love your site and will be back.See Ya

  2. michael m says:

    Is there a typo on the site or are there several mogule base sizes? The article starts off by defining E39 for Mogul & E26 for medium base, while later in the article E29 is also referred to as Moguul base.

  3. Conservation Mart says:

    Sorry for the confusion. Our mistake. E39 is Mogul Base, while an E29 base is known as the medium screw. Thanks for catching that!

  4. Howard says:

    In you article you indicate that a 3 way adapter is available for modul to medium bulbs. I have been looking for an ANSI E39D to E26D (three way bulb) adapter for two years. Please advise us of a source. Thanks

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  6. clif mccormick says:

    Thanks for the article.

    Do you have a source for a CLF replacement for a 3-way 100/200/300 mogul base lamp? I have several antique lamps that take these old monster bulbs and I would love to update them, but do not want to give up 3-way capability.

    Thanks Again!

  7. Conservation Mart says:

    Clif, thanks for the feedback!

    Unfortunately, we don’t have any 3-way mogul base bulbs. The mogul base CFLs that we carry are all of the single-wattage variety.

  8. Richard Washburn says:

    You said that you only carry single wattage mogul base cfl bulbs. But do you know of a source for a 3 way mogul to d=reduce to a 3 way standard?

    “you can get a converter to use a 3-way E26 light bulb in a 3-way E39 base bulb lamp.”

  9. Conservation Mart says:

    Richard, we unfortunately do not have a list of stores selling these converters. We can say there are a number of retailers, primarily online, who sell them. We suggest doing a quick online search for them and a list of stores selling converters as well as the prices they are listed for will come up.

  10. Michael Masi says:

    The ONLY one I saw so far. Please advise if you find them cheaper.

  11. Lisa Maria says:

    I too am unable to locate 3-way mogul converter. Despite ongoing search I’ve had no luck.

  12. Fernando Urrutia says:

    So E29 is the “standard” base (Edison style) and the E39 is the Mogul, it’s there on the market a base that it’s on between this two sizes? I work on retail and on one time a customer was looking for a “big lamp” (Mercury Vapor) and he mentioned that the Mogul base was just too big, but the standard base on mercury vapor was way too small for his light fixture (personally I believe he was not setting the lamp straight on the socket and that was the problem, it’s hard to do it when you are up on a 20 ft ladder!)…

  13. Conservation Mart says:

    Hi Fernando,
    We aren’t aware of a bulb base in between those two. It could be that the bulb was custom made for that specific fixture.

  14. Linda Doll says:

    Please tell me more about “you can get a converter to use a 3-way E26 light bulb in a 3-way E39 base bulb lamp.”



  15. Conservation Mart says:

    Hi Linda!
    Your local hardware or home improvement store may carry an adapter that screws onto the base of a standard-sized (E26) base bulb that will allow it to be used in a fixture that is for use with a larger base (E39) bulb.

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